1. Field of the Invention
The present invention relates to a biodegradable resin composition comprising polylactic acid and nanosheeted layered titanic acid, which is excellent in mechanical strength, moldability, dimensional stability and durability.
2. Description of the Related Art
In recent years, a biodegradable resin as an environment harmonizing-type polymer has been intensively studied. In particular, much attention is paid to polylactic acid as a raw material of plant which enables carbon neutral not only from a viewpoint of biodegradability but also from the cost and high physical property. However, a molded product therefrom has a problem that heat resistance, rigidity and impact resistance are inferior, thus, not leading to full-scale development. For solving such the drawbacks, techniques regarding a composition in which a layered silicate-based nanosheet treated with a swelling agent such as an ammonium salt and a phosphonium salt is uniformly dispersed in polylactic acid, and a film and a functional material obtained therefrom are disclosed, and it is shown that excellent heat resistance and rigidity, and gas barrier property are obtained while suppressing a specific gravity, by complexing polylactic acid and layered silicate (see, for example, JP-A No. 2003-82212 and JP-A No. 2003-73538).
However, in such the method, as a layered silicate-based nanosheet is dispersed better in polylactic acid, reduction in a molecular weight occurs at kneading, and a melt viscosity is reduced. Since reduction in a melt viscosity deteriorates molding processibility of, for example, a film, and further increases a thermal expansion coefficient under a high temperature, dimensional stability is deteriorated.